THE United States used deadly nerve gas in top secret operations during the Vietnam War, CNN and Time magazine reported yesterday.

Sarin, the same gas that was used by the Japanese cult Aum Shinri Kyo on the Tokyo underground in 1995, was used on a mission to kill US defectors, they reported. The Pentagon did not confirm the report, but it was confirmed by the top military officer at the time of the incident.

Operation Tailwind was a highly classified operation to find and kill American defectors in Laos in 1970. It was mounted by the shadowy Studies and Observation Group, who conducted "black operations" with unconventional weapons and unusual targets. Based in Kontum in Vietnam, they were ordered to find a group of US defectors in Laos. At the time, US forces were not supposed to be operating in Laos.

Their mission was to kill the defectors, who, it was feared, might disclose details of sensitive operations. "My orders were, if it's alive, if it breathes oxygen, if it urinates, if it defecates, kill it," said platoon leader Robert Van Buskirk. The village where the defectors were based was bombed with nerve gas. The commandoes then attacked the village where they found several people who they believed to be Americans. All were killed, including many women and children.

But on their way back, the soldiers were ambushed and cut off from the helicopters that would evacuate them. "The enemy was coming at us. We were out of ammo," said Van Buskirk. He radioed an Air Force controller for what they called "the bad of the bad". A flight of Skyraiders dropped gas canisters which killed all of the North Vietnamese and communist soldiers. Vomiting and convulsing, they died where they stood. "All I see is bodies," said Van Buskirk.

Though the Pentagon could not confirm the story, Admiral Thomas Moorer, Chairman of the Joint Chiefs of Staff in 1970, confirmed that in this mission and others to rescue airmen trapped behind enemy lines, sarin was used. "I would be willing to use any weapon and any tactic to save the lives of American soldiers," he told CNN and Time. Use of the gas would have been sanctioned by President Richard Nixon's national security team, he said.

The fact sarin had been used on the village before the attack as well as afterwards means, however, that civilians were killed as well as enemy troops. This was at a time when the US had pledged under the Geneva Protocol not to use chemical or biological weapons unless they had been used by an enemy first. It raises grave questions about subsequent US use of such prohibited weapons. The programme concludes that sarin may have been used more than 20 times.

Some of the Laos SOG team suffered after-effects from the raid. The gas masks which they were issued were, in some cases, defective. Sergeant Mike Hagen suffers from creeping paralysis in his extremities, one of the recognised symptoms of nerve gas damage. The SOG commandos were also issued atropine, a nerve gas antidote, CNN and Time reported.